Jets of solar-wind plasma commonly hit the Earth’s magnetosphere. Using data from the four Magnetospheric Multiscale (MMS) spacecraft, we show statistically that within jets the magnetic field is more aligned with the plasma flow direction than outside of these jets. Our study confirms prior simulation results, but it also shows that the average effect is moderate. The jets’ magnetic field is important with respect to their impact on space weather.

Terrestrial ion transport and total escape are synthesized, with stress on the high-latitude polar region and the inner magnetosphere where Custer significantly improved knowledge. After estimating the outflow flux and destinations, complicated ion dynamics in the inner magnetosphere was classified and summarized, through which more than half the O+ is finally lost to space. Together with direct escapes, total O+ escape is high enough to influence the evolution of the biosphere.

The mirror mode starts as a zero-frequency ion fluid instability and saturates quasi-linearly at very low magnetic level, while forming extended magnetic bubbles. These trap the adiabatically bouncing electron component which forms pairs near the mirror points. The large pair anisotropy causes further growth beyond quasilinear level. Including pressure equilibrium gives and estimate of the required pair density.

When the terrestrial magnetic field is disturbed, particles from the near-Earth space can precipitate into the upper atmosphere. This work presents, for the first time, numerical simulations of proton precipitation in the energy range associated with the production of aurora (∼1–30 keV) using a global kinetic model of the near-Earth space: Vlasiator. We find that nightside proton precipitation can be regulated by the transition region between stretched and dipolar geomagnetic field lines.

We describe a technique used to locate and classify critical points in 2-D flow fields at the solar photosphere obtained from the evolution of the line-of-sight magnetic field in a region close to the magnetic polarity inversion line of a fully emerged active region. We apply this technique to locate a particular kind of critical point associated to vortex flows, which are considered important, since they can twist and interweave the foot points of flux tubes and generate magnetic reconnection.

This paper originated from the lecture I gave as the Hannes Alfvén medalist at the EGU General Assembly in Vienna in spring 2018. The paper reviews various aspects of modern solar wind physics and elucidates the role Alfvén waves play in solar wind acceleration and turbulence, which prevail in the low corona and inner heliosphere. Our understanding of the solar wind has recently made considerable progress based on remote sensing, in situ measurements, kinetic simulation and fluid modeling.

A record has been found of an “aurora” observed on 27 October 1856 in the Philippines, practically at the magnetic equator. An analysis of this report indicates that it could belong to a “sporadic aurora” because of low magnetic activity at that time. We provide a possible physical mechanism that could explain the appearance of this sporadic, low-latitude aurora, according to the analyses on the observational report and magnetic observations at that time.

The physics of the magnetic mirror mode in its final state of saturation, the thermodynamic equilibrium, is re-examined to demonstrate that the mirror mode is the classical analogue of a superconducting effect in an anisotropic-pressure space plasma. Three different spatial correlation scales are identified which control the behaviour of its evolution into large-amplitude chains of mirror bubbles.

The novelty of this paper lies in the fact that it addresses the thermosphere–ionosphere coupling in a midlatitude site in north Africa. We have used Fabry–Perot measurements of thermospheric winds and wide-angle camera detection of ionospheric structures at an altitude of about 250 km. We have also used GPS data to extract the TEC over the studied area. We have focused our study on the 27 February geomagnetic storm.

The magnetospheric response to the solar wind is nonlinear. Information theoretical tools are able to characterize the nonlinearities in the system. We show that nonlinear significance ofDstpeaks at lags of 3–12 hours which can be attributed toVBs, which also exhibits similar behavior. However, the nonlinear significance that peaks at lags of 25, 50, and 90 hours can be attributed to internal dynamics, which may be related to the relaxation of the ring current.

We reveal previously unknown quasi-periodic (QP) VLF emissions at the unusually high-frequency band of ~ 7–11 kHz by applying the digital filtering of strong sferics to the ground-based VLF data recorded at Kannuslehto station (KAN). In one event, the spectral–temporal forms of the emissions looked like a series of giantbullets, with very abrupt cessation. In the second event, the modulation period was about 3 min under the absence of the simultaneous geomagnetic pulsations.

The question of whether mesospheric rotational population distributions of vibrationally excited OH are in equilibrium with the local kinetic temperature has been debated over several decades. We examine the relationship of multi-quantum relaxation pathways with the behavior exhibited by OH(v) rotational population distributions and find that the effective rotational temperatures of mesospheric OH(v) deviate from local thermodynamic equilibrium for all observed vibrational levels.

The sequence of phenomena consisting of solar flares, coronal mass ejections (CMEs), auroral substorm, and geomagnetic storms is mostly a manifestation of electromagnetic energy dissipation. Thus, first of all, it is natural to consider each of them in terms of a sequence of power supply (dynamo), power transmission (electric currents/circuits), and dissipation (mostly observed phenomena), i.e., as an input–output process and the electric current line approach.

Results from a high-altitude balloon experiment conducted from a low-latitude station in India are presented in this work. The objectives of this experiment were to probe and understand the processes driving the various electric field sources at low latitudes. During this experiment, electric fields in the range of 5–6 mV m−1 were observed at the balloon float altitude of 35 km. Atmospheric waves of few 100 km horizontal wavelength are suggested to be a potential source of these electric fields.

A new type of wave has been detected by the magnetometer of the Rosetta spacecraft close to comet P67/Churyumov-Gerasimenko. We provide the analytical model of this wave excitation from linear perturbation theory. A modified ion-Weibel instability is identified as source of this wave excited by a cometary current. The waves predominantly grow perpendicular to this current. A fan-like phase structure results from superposing the strongest growing waves in a cometary rest frame.

This study presents an investigation on the occurrence of fast flows in the magnetotail using the complete available data set of the THEMIS spacecraft for the years 2007 to 2015. First, basic statistical findings concerning velocity distributions, occurrence rates, group structures and key features of 16 000 events are presented using Superposed Epoch and Minimum Variance Analysis techniques.

The method of electric field mapping along geomagnetic field lines, derived in an accompanying paper, is applied to the International Geomagnetic Reference Field. Formulae for the geomagnetic field gradient tensor are derived and these are used in a software package developed to map the electric field. A number of examples are presented illustrating the method. The method will be of importance in conjugate studies of ionospheric convection when the external magnetic field can be neglected.

This paper introduces a new method for mapping electric fields in the magnetosphere along geomagnetic field lines. This is important for conjugate studies of electric fields measured in the ionosphere by SuperDARN radars, and at spacecraft carrying electric field probes. First elementary methods in a dipole field are reviewed and then the theory of of a new method described for general magnetic field models. The method is tested in a dipole model with a Harris magnetotail field.

Adaptive magnetospheric models based on THEMIS magnetic observations made at 6-9Re in the nightside magnetosphere are used to map the magnetically conjugate 30 and 80keV proton isotropy boundaries (IBs) to investigate the value of Kib=Rc/rc (magnetic curvature radius to particle gyroradius) in the neutral sheet at the IB generation place. For the most accurate mapping, the group Kib spread spans from 4 to 32; its median value is ~13, slightly larger than Kib8 expected for current sheet scatter.

About EGU

EGU, the European Geosciences Union, is Europe’s premier geosciences union, dedicated to the pursuit of excellence in the Earth, planetary, and space sciences for the benefit of humanity, worldwide. It was established in September 2002 as a merger of the European Geophysical Society (EGS) and the European Union of Geosciences (EUG), and has headquarters in Munich, Germany.